This invention relates to a device for sucking in and compressing at least one gas in a fuel cell system which has a fuel cell to which gaseous fuel and an oxidizing gas are supplied.
A drive unit in a vehicle which has an electric driving motor, a fuel cell, a fuel tank, a water store, an evaporator and a reformer is known. The fuel tank contains methanol which, with water from the water store, is converted into the gaseous state in the evaporator and is then passed to the reformer, in which substantially hydrogen, carbon dioxide and carbon monoxide are formed when heat is supplied by means of a catalytic burner. The carbon monoxide can be oxidized using an oxidizing agent. The hydrogen-containing fuel gas from the reformer is fed by means of a compressor to the fuel cell, which comprises a fuel cell stack in which a large number of individual fuel cell modules are integrated. Air is fed to the fuel cell by means of a further compressor. In the fuel cell, electrical energy for the electric driving motor is generated from the hydrogen and the oxygen of the air (See German document DE 44 12 450 A1).
To operate, a fuel cell requires sufficiently purified gas and/or a gas mixture with respect to the fuel gas and the oxidizing gas, which is in many cases air. This means that impurities in the gases have to be eliminated. Examples of impurities of this type, which damage the fuel cell system, may include particles, aerosols or polluting gases. Filters connected upstream of the compressors are used for the gas purification.
For compression it is possible to use centrifugal compressors, which in operation generate high-frequency noise, which is unpleasant. To reduce environmental pollution, this noise has to be muffled. It is known to arrange deep-tuned Helmholtz resonators in exhaust mufflers of motor vehicles. Since Helmholtz resonators for muffling noise generally comprise a plurality of cylindrical chambers connected to one another by tubes, they increase the overall volume of a gas-routing section. In particular in mobile devices, it is desirable to minimize the space taken up by gas-routing systems.
There is a known sound-muffling tube for carrying gases in which sound reflectors which reduce the passage cross section are arranged at intervals in the axial direction of the tube. The reflectors are formed by a corrugated tube wall, which in addition to the corrugation also includes elements which disrupt the propagation of sound (See German document DE 35 05 401 A1).
In another known device for reducing resonance effects in pipelines through which gases flow, the gas flow is distributed between in each case two identical, substantially parallel tubes, at least one of which is provided with a perforation over which a covering hood is fitted (See German document DE 94 00 428 U1).
Finally, a porous muffling hose for muffling intake noise in internal combustion engines is known (See German document DE 196 35 799 A1). The muffling hose is formed from a roll of a flat mesh material of weldable plastic filaments which consist of a single material. Since the muffling hose is longitudinally elastic, it does not transmit any longitudinal vibrations in the intake section of the corresponding internal combustion engine.
This invention addresses the problem of providing a device for sucking in and compressing at least one gas in a fuel cell system in which the structure-borne sound originating from the respective compressor is muffled in a simple and space-saving way.
The problem is solved according to the invention, in a device for sucking in and compressing at least one gas in a fuel cell system which has a fuel cell to which gaseous fuel and an oxidizing gas are supplied, by virtue of the fact that a compressor for the gas is connected at its entry or gas inlet to a gas filter system via an elastic, sealed gas-routing passage made from textile material. In the device according to the invention, the sound waves emanating from the compressor when the latter is operating are muffled both by the elastic gas-routing passage or hose and by the gas filter system. The latter prevents sound waves which still arrive, for example, at the filter-side end of the gas-routing passage from being able to pass to the outside without being impeded.
In particular, the gas-routing passage includes fibers which are sealed off so as to prevent the penetration of gases from the space outside the gas-routing passage by means of an elastic coating. The coating may consist of a plastic, e.g. an elastomer, or of a metal.
In a preferred refinement, a gas-routing passage formed from porous, textile material is provided upstream of the gas filter system and connected to the gas inlet of the gas filter system. In this device, which constitutes an independent inventive configuration, the gas which is sucked in is pre-filtered. Furthermore, the sound waves, which have already been greatly muffled by the elastic gas-routing passage between compressor and gas filter system and by the latter, are muffled still further, so as to achieve a particularly good reduction in noise. Moreover, the porous gas-routing passage upstream of the gas filter retains particles in the gas which is sucked in, so that they cannot enter the filter system.
It is expedient for the textile material of the porous gas filter passage to be coated with at least one active substance which is ready to react with respect to at least one gas. It is in this way possible to reduce the concentration of at least one polluting gas which is contained in the gas that is sucked in and is undesirable for operation of the fuel cell even upstream of the filter system.
In the text which follows, the invention is described in more detail on the basis of an exemplary embodiment illustrated in a drawing, from which further details, features and advantages will emerge.